Sutton D108 Heavy Duty Cobalt Jobber Drill Bit 2.5mm, Carded

The Sutton D108 is a 2.5mm jobber drill bit pressed from 5% cobalt high speed steel, made for the jobs where an ordinary HSS bit gives up. Cobalt keeps its hardness at higher cutting temperatures, so the edge survives longer in hard steel, stainless and high tensile plate.

Sutton build this range with a thicker core than a standard jobber drill. That extra web is what stops the bit flexing and wandering once it bites into a hard material, and it is the reason this range is the one to reach for when a plain HSS bit starts to squeal and dull.

What this bit suits

• Hard and high tensile steel
• Stainless steel, including sheet and plate
• Cast iron
• General engineering and maintenance work where bit life matters more than the cheapest price

Specifications

• Diameter: 2.5mm
• Overall length: 57mm
• Flute length: 30mm
• Material: 5% cobalt high speed steel (HSS-Co)
• Point: precision split point for a self centring start
• Finish: colour tempered for quick size identification
• Supplied: single bit, carded
• Sutton item number: D1080250

Why cobalt instead of standard HSS

Standard HSS starts to lose its temper once the cutting edge gets hot, and drilling stainless or hard steel heats an edge quickly. Cobalt alloyed steel holds its hardness further up the temperature range, so the bit keeps cutting instead of rubbing. The practical result is cleaner holes, less pressure needed on the drill, and far fewer resharpens over the life of the bit.

If you are drilling mild steel all day, a standard HSS jobber drill will do the job for less money. Cobalt earns its place when the material is hard, when it work hardens, or when a broken bit in the middle of a job costs you more than the bit did.

Drilling tips

• Use a cutting fluid or at minimum a few drops of oil on stainless. It makes a large difference to edge life.
• Keep the speed down and the pressure steady. Cobalt cuts on pressure and torque, not on speed.
• Use a centre punch or a pilot bit on smooth surfaces so the split point has something to bite.
• Let the drill do the work. Leaning on a 2.5mm bit is how they snap.

Frequently asked questions

What does 5% cobalt actually mean?

The steel the bit is ground from contains 5% cobalt, alloyed through the whole bit rather than coated on the surface. That is why a resharpened cobalt bit is still a cobalt bit, while a coated bit loses its coating the first time it touches a grinding wheel. It is the reason cobalt bits cost more and last longer in hard materials.

Can I use this bit in a cordless drill?

Yes. A 2.5mm bit is well inside the capacity of any 18V cordless drill. Run it at a moderate speed and let the drill’s torque do the work. Cobalt wants pressure rather than speed, which suits a cordless drill well.

Will it drill stainless steel?

Yes, and this is the material where the cobalt content earns its keep. Use a slow speed, firm steady pressure and cutting fluid, and do not let the bit spin in one spot. Stainless work hardens if you rub it instead of cutting it, and a work hardened surface is much harder to get through.

What is the difference between a jobber drill and a mechanics length drill?

A jobber drill is the standard length bit, 57mm overall at this size, and covers the great majority of workshop and site drilling. A mechanics length drill is shorter and stiffer, for tight spots and for drilling where a longer bit would flex.

Is this a single bit or a pack?

Single bit, carded. If you go through this size regularly, the trade packs work out cheaper per bit and are worth a look in the drill bits category.

Need to finish the job

Cobalt jobber drills pair naturally with a countersink for a flush finish, and with a drill and countersink set if you are piloting and deburring the same holes. For larger holes in the same material, see our range of holesaw arbors.

We supply the Sutton D108 range for delivery Australia wide, and you can collect from our Truganina trade counter if you are local to Melbourne’s west.